doi:10.3850/978-981-08-6396-8_P079

ABSTRACT

The construction works on the Circle Line Project (CCLP) was halted in April 2004 when a section of the cut and cover tunneling works along Nicoll Highway (NCH) collapsed. After the collapse, Land Transport Authority of Singapore (LTA) has decided to realign the NCH Station and tunnels as the risks could be better mitigated. The realignment of NCH Station and tunnels presented a number of unique challenges to be overcome during the planning, design and construction stages. These included tunnelling through the previously constructed bored tunnels and tunnelling in the soft marine clay, which in some locations was still undergoing consolidation settlement, and the control of ground movement due to deep excavation in the soft Marine Clay. These potential problems were identified well in advance and the risks were mitigated or managed by putting appropriate solutions in place. These solutions utilized a combination of previous Singapore experience and new techniques, allowing the tunnelling & excavation works to progress as planned. This paper will present these challenges that have been overcome to complete the project successfully.

Keywords: Bored tunneling, Deep excavation, Realignment, Risk management, Design & construction challenges.

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